Pseudopotential calculation of the structure and thermodynamics of liquid alkali metals with a square-well model as a reference system

We investigate the applicability of a variational method with a new reference system (square-well model) to the description of the structure and thermodynamics of liquid metals. An expression for the system entropy for a one-component fluid is derived. The three parameters of the model (the hard-sphere diameter and the width and depth of the square well) are determined by the variational method using the local pseudopotential approximation. The approach is used for liquid Na and K, and the calculated results are compared with experiment. It is shown that the approach can provide a realistic description of the properties of liquid metals.